rxjs-interop/source/to-observer-spec.ts

Observable interop helpers for RxJS

/**
 * @license Use of this source code is governed by an MIT-style license that
 * can be found in the LICENSE file at https://github.com/cartant/rxjs-interop
 */

import { expect } from "chai";
import { toObserver } from "./to-observer";

describe("toObserver", () => {
  it("should return non-partial observers", () => {
    const observer = {
      complete() {},
      error() {},
      next() {},
    };
    const result = toObserver(observer);
    expect(result).to.equal(observer);
  });

  it("should support partial observers", () => {
    const observer = {
      next() {},
    };
    const result = toObserver(observer);
    expect(result).to.not.equal(observer);
    expect(result.next).to.be.a("function");
    expect(result.error).to.be.a("function");
    expect(result.complete).to.be.a("function");
  });

  it("should bind a partial observer's context", () => {
    let receivedThis: any;
    let receivedValue: any;
    const observer = {
      next(this: any, value: number) {
        receivedThis = this;
        receivedValue = value;
      },
    };
    const result = toObserver(observer);
    expect(result).to.not.equal(observer);
    expect(result.next).to.be.a("function");
    result.next(42);
    expect(receivedThis).to.equal(observer);
    expect(receivedValue).to.equal(42);
  });

  it("should support an undefined argument", () => {
    const observer = toObserver(undefined);
    expect(observer.next).to.be.a("function");
    expect(observer.error).to.be.a("function");
    expect(observer.complete).to.be.a("function");
  });

  it("should throw if an error method is not specified", () => {
    const observer = toObserver({
      complete() {},
      next() {},
    });
    expect(() => observer.error("Kaboom!")).to.throw("Kaboom!");
  });
});